This tank was marked as filled in December 13, 200S and was

installed in the aircraft some time after that date by the

manufacturer. The LearJet service center did a historical

research and discovered that they had other aircraft with the same

problem. (A/c 45-282 discovered on May 23, 2006 and Ale 4SJ208l

When and were the halon had discharged could not be determined and

no evidence of agent was located so a slow leak can only bJ

detected by the indicator on the bottle. Examination of th~ gauge

discovered that with a little jarring it was possible to rqtate

the dial inside the indicator. This was apparent far all of the

bottles in question that the crimps of the dial faces inside the

gauges were inadequate. It is therefore impossible to reli~bly

determine the level of the fire retardant for the bottle.

The second issue of concern was that when the technician fired the

Squib the tube leading from the bottle was not strong enough to

withstand the forces involved. The tube showed evidence of blow

out and impact marks on the inside of the ~ube. The tube was

installed by the manufacture and is made of aluminum instefd of the

normal steel. Learjet Inc repair center also submitted an M or D

for this issue. It is apparent that the holes in the tube during

discharge were suffeiciant enough to prevent the blowout disk

from rupturing.

It is then recommended in the interest of public safety that all

of the aircraft that have one or more Pacific Scientific fire

bottles, part number 33100021-1 be inspected for discharge by

weighing the bottle until such time as a better design for, the

gauge is in place. In this current configuration, should the

Halon bottle leak down or the squib charge fire unknowingly, the

empty bottle would not be detected during a normal walk arbund.

It is also recommended that the discharge tubes be replace~ with

a material that would withstand the pressures and heat of t fire

bottle discharge. This has the potential of allowing the

aircraft to be dispatched without the needed fire suppress'on

available. It is very important that the flight crews can be

assured that should there be a need to extinguish a fire ih flight

that the bottles have enough retardant to prevent. a total] loss of

the aircraft.

INTERIM RESPONSE OF 09-28-2006,

This is an initial response to ~AA Safety Recommendations

06.121 and 06.122. The Wichita ACO has requested Learjet

investigate the areas discussed by the recommendations and

review the appropriateness of implementing these I

~:~~mmenda'iona. We will keep you appriaed of any action Ie

If you require further assistance please do not hesitate to

tAA -2-GID- CID-7fc,

;;;! u Ic> - NM - 0 OJ S--A D

Jc~/_/ I -;;-
contact James Ga!stad at (316) 946-4135 or the Safety

Recommendations Program Manager, Shardul Panchal at (425)

227-21]4.

INTERIM RESPONSE OF 10-10-2007:

We received the initial Learjet Inc. position on the subject Safety

Recommendations. The Wichita ACO recognizes the merit of Learjet's

question about the absence of Halon as a pre-requisite factor for damage to

the discharge line on Ale 45-310. Data is needed to show that line damage is

limited to bottle discharge without Halon. What is the threshold level of

charge and Halon required for a discharge to fracture the blowout disk?

Do the blow-out disks fracture correctly? Was the correct squib

installed in the bottle? Did the squibs expend the correct amount of

energy? Is ICA information needed to assure discharge line integrity

following discharge of an empty bottle? Full bottles? I

Following the inadvertent discharge on AIC 45-3 10, the tank indicator

showed full and the dial face staking was noted to be inadequate.

Subsequent information identified that the epoxy bond between the dial

face and gauge was also inadequate. Is the dial face design adequate?

Staking the dial face after the epoxy was cured was identified as a

process error to be corrected. Given that the epoxy bond was broken due to

a manufacturing process error, why did the staking fail to retain the dial

face? Is a process or design change needed for the dial facb staking?

How many and which aircraft are affected by each defiCienCY!"

What is the response from Pacific scientific to Learjet's tery to

determine the scope and impact on the entire Learjet fleet? What supplier

control activity has Learjet initiated with Pacific scientific?

It is our intent to proceed as identified above. At this tiLe, we believe

that corrective action based on the existing available information would

be incorrect. Additional information is needed to interpret the incident

defined in the SR. With many other cas activities and limits to our

resources. we believe that the approach outlined above will provide a

thorough examination of the incident and any associated fire extinguishing

bottle certification or type design issues. We will propose any corrective

action deemed necessary as soon as it is practical to do s6 in the course of

our investigation of these Safety Recommendations. We will provide another

status update prior to October 31, 2007.

INTERIM RESPONSE OF 03-10-2008:

This is a follow-on response to SRs 06.121 and 06.122 concerning

Pacific Scientific fire extinguishing bottles on Learjet Mbdel 45

airplanes. The Wichita Aircraft Certification office (ACO}j is working

with Learjet to resolve the issues identified in ADO letter L1 15W-08-

123 dated February 23, 2008. The ACO plans on an acceptable resolution

from Learjet by June 2008 at which time we will provide a status update.

If further discussion on this subject is needed, please contact James

Galstad of the ACO, at (316) 946-4135 or Shardul Panchal of the Safety

Management Branch, P~-117, at (425) 227-2134.